Precast concrete block joint



v. LEONTOVICH PRECAVST CONCRETE BLOCK JOINT.

Nov. 4,- 1 952 Filed April 26, 1949 4 Sheets-Sheet 1 INVENTOR VALEAMNlEo/vro V/CH ATTORNEY N 1952 v. LEONTOVI CH ,6

. PRECAST CONCRETE BLOCK JOINT Filed April 26, 1949 I 4 Sheets-Sheet 2.INVENTOE VA LEE/AN LEo/vTov/cH v BY ATTORNEY 1952 v. LEONTOVICH2,616,284

PRECAST concasm BLOCK JOINT Filed April 26, 1949 I I 4 Sheets-Sheet :s

.INVENTOR I/AI.ER/A/V LEONTOV/CH A TTORNEY Nov. 4, 1952- v. LEONTOVICHPRECASTCONCRETE BLOCK JOINT 4 Sheets-Sheet 4 Filed April 25, 1949 H m VWmm 7 mm. NM w n E Y y B 3 no ATTORNEY Patented Nov. 4, 1952 UNITEDSTATES PATENT OFFICE PRECAST CONCRETE BLOCK JOINT Valerian Leontovich,Palo Alto, Calif.

Application April 26, 1949, Serial No. 89,701

6 Claims. 1

This invention relates to a means for connecting precast concretebuilding blocks having reinforcing rods embedded therein, so as to formout of the plurality of said blocks a monolithic unit of uniformstrength.

The use of precast concrete blocks in building construction was proposedmany years ago, but has not received general acceptance as yet. One ofthe main reasons for failure to gain the general recognition andacceptance was, and is, the lack of reliable and simple connecting meansbetween the adjoining precast blocks which would provide proper tensileand fiexure connection therebetween. It may be illustrated by thefollowing example: a precast horizontal member is designed for resistingmoment in accordance with the formula wherein W and L are unit load andthe span of a beam,-respectively. However, if the same member is splicedwith another member, or its ends are affixed, the resisting moment ofsuch member is calculated in accordance with the formula or less.Therefore, by providing the continuity of a given precast concrete beam,the same may be built only of two-thirds of the simple beam moment, thuseffecting considerable economy in their construction.

This fact has been realized for a long time, and many attempts have beenmade to provide a simple and eflicient joining means for two adjacentprecast concrete members by connecting the same by special fittings,welding etc. But all such attempts did not-succeed for the reason ofbeing either impractical, or too costly.

Furthermore, the numerous inserts which were used for splicing saidprecast concrete members were incapable of transferring the full tensilestrength of one member to another, which is of utmost importance, as thesplicing member should not only be capable to withstand the load equalto the ultimate capacity of the reinforcing rod in said splicing member,but the bonding capacity of the connection at the initial slippreferably should be not less than the said ultimate capacity of therod.

Another object of this invention is to provide a new means forconnecting adjacent prefabricated concrete blocks by which the same areunited to provide structural continuity of uniform tensile or flexuralstrength.

Another object of this invention is to provide a new means forconnecting several adjacent prefabricated concrete blocks by which thefull tensile or fiexural strength of one block is transmitted to others.

Still another object of this invention is to provide a new connectionbetween precast concrete blocks, in which free ends of reinforcing rodsof one block are introduced into special jackets embedded in the otherblocks or blocks, whereupon said jackets are filled with a binder, suchas cement, or grout; said jackets being of such design as to createwedging action upon the end of the reinforcing rods embedded therein,when a force is applied to pull said rods out of said jackets.

Another object of this invention is to provide a new connection betweenadjacent prefabricated concrete blocks comprising a jacket in form of aplurality of superimposed frusto-conical sections embedded in one of theblocks, said sections tapering toward the open end. Said jacket isdesigned to admit a free end of a rod embedded in the other block,whereupon the jacket is filled in with cement, grout, or special groutand permitted to set.

Another object of this invention is to provide a special grout forfilling said jacket.

Still another object of this invention is to provide a new anchoringmeans for connecting to a concrete block individual rods, stubs, dowels,bolts, swedge bolts and the like.

Other objects and advantages will appear as the specification proceedsand the particular features of the invention will be specificallypointed out in the appended claims.

This invention is illustrated in the accompanying drawing in which:

Fig. 1 is a vertical cross-section through a concrete block containing ajacket.

Fig. 2 is a vertical cross-section through a concrete block having areinforcing rod protruding above the top surface thereof.

Fig. 3 is a cross-section through a concrete block showing a depressiontherein in form of a jacket shown in Fig. 1.

Fig. 4 is a vertical cross-section through two concrete blocks splicedin accordance with the teachings of this invention.

Fig. 5 is a horizontal section taken along the line 5-5 of Fig. 4.

- Fig. 6 is a side view of one half of the modified jacket.

Fig. 7 is a plan view of the modified jacket.

Fig. 8 is a perspective view of two concrete blocks ready for splicing.

Fig. 9 is a side view of three spliced concrete blocks.

Fig. 10 is a horizontal cross-section taken along line II0 of Fig. 9.

Fig. 11 is a plan view of Fig. 9 looking along the line II-II, and aFig. 12 illustrates how a hook may be imbedded in a block.

In general, I provide a jacket comprising a plurality of frusto-conicalsections superimposed upon each other and tapering toward the open endthereof. The jacket is embedded in a concrete block with the open endthereof flush with the side facing an adjoining block to which the firstblock is to be anchored. A passage is provided in the first mentionedblock leading from a side thereof to the other end of said jacket,

through which passage cement, grout or other cementitious material maybe poured into the jacket.

The second mentioned block carries a reinforcing member whichhereinafter shall be referred to through the specification and claims asa rod protruding beyond the surface of said block a certainpredeterminate distance. The free end of said rod is located opposite tosaid jacket and is adapted to enter the same for the purpose of beinganchored therein, when said blocks are placed in proper relation.

After the free end of said rod is introduced into the jacket and theblocks put in proper relation, cement, grout or other cementitiousmaterial is poured into the jacket through said passage and saidmaterial is allowed to set.

The jacket material is so chosen, that the cementitious material doesnot adhere thereto, but does adhere to the rod. Whenever a force isapplied to the rod tending to pull said rod out of said jacket, saidforce is transmitted by said rod to the cementitious material around thesame, as the latter is strongly bound to said rod. The said material,being free from adhesion to the jacket, has tendency to slip in relationto said jacket. The jacket being surrounded by monolithic reinforcedconcrete, cannot expand and reacts with passive compressive forces.Hence, the slightest slip of the cementitious material in the jacketresults in wedging action upon said material due to the frusto-conicalshape of the jackets sections, which action is evenly distributed alongthe whole length of said jacket, and is evenly transmitted upon said rodby said material. The greater pulling force is exerted on said rod, thegreater compression is produced on said rod by said material, due tosaid wedging action. Hence, the end of the rod is securely locked insaid jacket, thus locking both blocks together.

The same principle of using a wedging force is employed in attaching astub, dowel or bolt to a precast concrete block, or a wall.

By numerous experiments I have found out that copper, brass, aluminumand galvanized steel are suitable materials for the jacket, as they arecomparatively cheap and ductile, and are repellant to cement, grout andother cementitious materials, The slope of the frustrums of the sectionsisgpreferably 3-15, the smaller the slope the greater wedging action isdeveloped by its sections, subject to limitation by slippage between thegrout and the jacket. For illustration purposes, I have shown 4 Figs.1-4 and 8 two concrete prefabricated blocks I and 2, which are to be setone upon another and spliced. The lower block I has a plurality of rods3 therein, the ends of which extend beyond the top surface 4 of saidblock a certain predeterminate distance. The rods 3 are of structuraltype and have a plurality of indentations and embossments thereon forthe best possible connection and uniting with concrete. A number ofhorizontal reinforcing members I is also imbedded in said block.

The upper block 2 has also a plurality of reinforcing rods 8 located inclose proximity to the corners of said block- The rods 8 are preferablytied by the horizontal members 9.

The blocks l and 2 are connected by a connector II] which comprises aspecially designed jacket II containing a free end of the rod 3 anchoredin said jacket by means of grout or other cementitious material.

The jacket II is located in said block 2 opposite each rod 3 of theblock I, said jacket being opened at its bottoms. Each jacket IIconsists of a plurality of frusto-conical sections I2 superimposed uponeach other, the narrow end I3 of each section being closer to theopening IA of the jacket, than its wider end IS. The wide end It of eachsucceeding section is connected to the narrow end I3 of each precedingsection by a round shoulder IT. The last section I2 is formed at itsbottom into a long cylindrical part I8. The top of the jacket II isclosed by a cap I9, which carries a tube H. The jacket II is preferablymade of cheap ductile metal which is repellant to cement and cementgrout, such as copper, brass, aluminum and galvanized steel, which whileinexpensive, possess said qualities. The slope of the frustrums of thesections I2 is preferably between 3 to 15, however greater slopes may beused.

The jacket II may be integral, or consist of two or more parts, whichmay be connected together by welding, soldering, or bolts, or otherwise.In Figs. 6 and 7 I show a jacket 25 -made of two symmetrical halves 26and 21 having flanges 28. The latter may be welded, spot-welded, boltedor otherwise secured to each other for the purpose of making a completejacket.

The cylindrical part I8 is specially provided for the purpose ofavoiding high concentration of stresses near the blocks surface.

The purpose of the cap I9 is to close and keep the jacket I I closedwhile the block is being made. The tube 2I serves as a passage for groutinto the jacket II. Said tube 2| is preferably made with a slipextension 22 which permits increasing or decreasing the length of thetube so that the end of the tube may be positioned flush with the sidewall of the block The rod 3 is introduced into the jacket II and isplaced concentrically thereto. The block 2 is placed on the block I,whereupon grout is poured into the jacket II through the tube 2| and isallowed to set, to form a grout mold 23 which adheres to the rod 3 butdoes not adhere to the walls of said jacket.

When a force is applied to separate said blocks I and 2, the pullexerted on the rod 3 and transmitted to the grout, will produce wedgingeffect upon the latter due to the shape of said jacket,

which effect will be evenly distributed along the length of the jacketand evenly transmitted upon the rod 3, thus wedging the rod 3 in saidgrout.

; It is desirable to have the horizontalmembers 9 gar-seer closelyspaced around the jacket fl in order to counteract radial pressureexertedby thejacket, or the jackets, on surroundingconcrete.

Fig. 3 shows a concrete block 30' having a depression 3| made in form ofajacket by some form which, after the concrete block sets, may be takenapart and out of said depression. A passage 32 is provided in said blockfor" the purpose of pouring grout into said depression after a rod, orsome other member, is introduced thereinto.

By eliminating a metallic jacket aconsiderabl'e saving may be achieved;and the depression 3|, having the same form as the jacket, will react onthe grout therein exactly the same as the jacket. The Wall of thedepressiontl should be covered with some grout repellent compositiontoprevent the adherence of the groutto the concrete block.

Figs. 9-11 illustrate the application of the connectors for connectingtwo beams 40 and 4| with a column 412 wherein the ends of the beams reston said column. For the purpose of connecting the two beams together,the beam 48 is provided with four jackets 43 embedded in the end thereoffacing the beam ll. The latter beam has four reinforcing rods 4d locatedopposite said jackets, so that said rods enter said jackets. A pluralityof reinforcing members 56 arranged around said jackets is provided inthe beam 40 to take care of the stress-eswhich may develop therein. Therods M are anchored in said jackets by grout poured through the passages41. I

For the purpose of attaching the beams 40 and 4! to the column t2, thelatter is provided with four jackets 38 adapted to receive the rodsanchored in said beams. The beam 40 has two reinforcing rods 49 embeddedtherein, the free ends of which enter the jackets 48 after the same arefilled with grout. The beam 41 preferably has a pair of verticallyarranged jackets 5| extending practically the whole thickness of saidbeam. Upon splicing the beam 40 with the column 42, the beam 4| is movedin so that its reinforcing rods 44 enter the horizontal jackets 43, andthe jackets 5| are aligned with the jackets 4B, whereupon shortreinforcing bars 52 are dropped into said jackets and grout poured in.The jackets 5| are surrounded with a reinforcing member 53 in the formof a spiral.

The jackets 43 are reinforced by a plurality of reinforcing members 56.Grout is also poured and fills in the spaces between said concretemembers, which is preferably about one half inch, for the purpose ofproviding flexibility between the same.

Fig. 12 illustrates how a bolt, a hook, or the like, may be secured to aconcrete block, or a wall. A jacket to is provided in a block 6|. Saidjacket may have a passage 62 leading from the inner end of said jacketto the outside surface of the block for the purpose of introducing groutinto said jacket, if for some reason grout cannot be introduced throughthe open end of said jacket. A hook 63, or bolt, or the like, isinserted in the jacket and grout is forced in. Upon setting of groutsaid hook 63 is securely anchored in the block.

It is understood that in every connector, the jacket may be dispensedwith, and a depression may be provided in the concrete block instead ofsaid jacket, providing said depression has a form adapted to wedge groutand the rod contained therein, thereby greatly increasing the anchoringpower of the connector.

In some cases for some special classes of con-' crete-Where extremedurability and strength is" required, I prefer to use a special groutwhich is comprised of cement, water'and small particles of quenchedsteel, for instance nail whiskers, all mixed in any desired proportion.The preferred composition of this grout consists asfollowsz one part ofcement by weight, to one to five parts of said steel particles. Amountof water and sand depends upon the desired degree of plasticity ofgrout.

I found experimentally that to bear the tensile capacity of anchoredrod, the grout in the jacketshould not only withstand compression andshear, but mainly bear the extreme pressure exerted on the grout by theprojections and deformations of the rod. quenched steel particles, suchas nail whiskers, when added to the grout in the above proportion,

make thegrout extremely strong in bearing and consequently permit todevelop high tensile capacity in the connector.

I claim: t

1. In a joint between two precast blocks, a rod anchored in one of saidblocks and having a free end extending therefrom, the other of saidblocks having an opening on the side opposit said one block, a jacket insaid opening comprising a plurality of frustrums superimposed upon oneanother and tapering toward the side opposite said one block, said freerod end extending into said jacket, a binder filling the chamber andsurrounding said rod end in said jacket, said jacket having a straightcylindrical section near said open block side, a cover closing theopposite end of said jacket, said cover having an opening therein toadmit said binder to said jacket, a pipe embedded in said other blockand leading from said opening in said cover to a side of said othervblock, said pipe constituting a passage for the delivery of said binderinto said jacket, said jacket having a binder repelling inner surfaceallowing slippage between said surface and said binder.

2. A connection between precast blocks, said connection including areinforcing rod embedded in one of said blocks and having a free endextending beyond said one block, a jacket embedded in another of saidblocks, said jacket having an open end at that of the block sides whichfaces the one of said blocks, said jacket comprising a plurality offrusto-conical sections superimposed upon one another and having thesmaller ends of their frustrums disposed toward the open end of saidjacket, said free rod end extending through said open end into saidjacket, a binder around said free rod end filling said jacket, saidjacket having an inner wall surface repelling said binder to allowslippage between said binder and said jacket under a pulling force,whereby wedging action is effected by said binder upon said free rodend.

3. A joint between two precast concrete blocks, said joint comprising arod embedded in one of said blocks and having a free end extendingbeyond said one block, the other of said blocks having a depression oflarger cross section than that of said rod end and having an open end,said free rod end extending through said open end into said depression,said depression being in form of a plurality of superimposed frustrumstapering toward the open end of said depression, a binder filling thespace between said free rod end and the walls of said depression and ameans on the walls of said depression allowing slippage between saidbinder and said walls, whereby said I'also found that the free rod endextending into said depression is subjected to a wedging action by saidbinder, when a pulling force is exerted on said free rod end.

4 4. A joint connecting two precast blocks, said joint comprising a rod,one end of which is embedded in one of said blocks and the other end ofwhich extends beyond said one block, the other of said blocks having acavity open at the block side facing the one block, said cavity being oflarger cross section than that of the other rod end and receiving saidother rod end, a binder around said other rod end in said cavity fillingthe latter, said binder having the form of a plurality of superimposedfrustrums tapering toward the opening of said cavity and means on thewall of said cavity preventing adhesion of said binder to said wall andthereby permitting slippage between said other block and said binderunder a pulling force, whereby a wedging action takes place on saidother rod end within said binder.

5. In a concrete block, a rod anchoring means, said block having acavity formed in one side of said block, a rod having a free rod end,said cavity receiving said free rod end, a binder embedding said freerod end in said cavity and filling the latter, said binder being in theshape of a wedge tapering toward said one side of said block, means onthe walls of said cavity preventing adhesion of said binder to saidcavity walls and thereby permitting slippage of said binder in relationto said block under a pulling force, whereby a wedging action isefiected on said rod end within and by said binder.

6. In a joint between two precast blocks, a rod anchored in one of saidblocks and having a free end extending therefrom, the other of saidblocks having an opening on the side opposite said one block, a jacketin said opening comprising a plu- REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Date Number Name 531,520 Eddy Dec. 25, 1894876,985 Malancon Jan. 21, 1908 1,112,069 Kennedy Sept. 29, 19141,349,901 Meischke-Smith Aug. 1'7, 1920 1,355,572 Ross Oct. 12, 19202,165,686 Suiter et a1 July 11, 1939 2,396,045 Henderson Mar. 5, 19462,420,427 Henderson May 13, 1947 FOREIGN PATENTS Number Country Date357,422 Great Britain Sept. 24, 1931

